The disposal of waste such as trees, brush, yard waste, etc. is a major concern of the municipal, commercial and private sectors. Various types of recycling equipment and techniques are in use or have been proposed to dispose of such waste, all with varying degrees of success.
One method is to transport and to bury the waste in a landfill. However, landfill sites are becoming scarce and those remaining are cost prohibitive especially in rapidly growing urban areas. In addition, even if suitable sites can be found, they are often at a distance that makes transportation costs prohibitive. Since vegetation waste makes up approximately 40% of the bulk typically buried in landfills, most large cities require that the waste be separated from conventional garbage for purposes of mulch and compost manufacture in an effort to recycle the waste.
Each year there are tens of thousands of acres of land cleared of trees, brush, etc. for development and millions of tons of yard waste (small branches, leaves, grass, etc.) produced. Reducing the amount of such waste being buried or mulched would significantly reduce the pressure on the existing landfills and delay the need for opening new landfill sites. In addition, landfills are a relatively inefficient method of recycling. Being simply buried at one site, the economic potential of the waste material is never fulfilled. Also, solid waste landfills are diminishing rapidly and permits for new sites are difficult to secure.
Another waste material that presents challenges with regard to disposal is animal carcasses. In the past, diseased animal carcasses were usually buried and forgotten. Little was known about the agents that caused the deadly diseases which have wiped out many herds of cattle and entire chicken farms. It has been discovered that certain pathogens can survive for over fifty years in the soil where they have been buried along with animal carcasses that perished from the disease.
One alternative to landfills has been to incinerate the waste material. With regard to wood and vegetation wastes, this produces an ash residue which is extremely high in natural nutrients beneficial for plant growth. When the ash is mixed with compost and varying amounts of soil, a range of products from high-grade potting soil to top soil are developed. Open burning of the vegetation waste on site is the simplest and most cost effective way of incinerating the waste material. However, due to the many environmental limitations imposed by federal, state, and local jurisdictions, open burning is not always feasible or possible. With regard to the disposal of animal carcasses, the only known practical approach to the elimination of diseased carcasses is high temperature incineration.
Some open pit incineration has been made possible through the use of air curtain incinerators such as the device disclosed in U.S. Pat. No. 4,756,258. In an open pit incinerator, the waste is loaded into a fire pit through an opening and then ignited. High velocity air from a manifold positioned along the opening is then blown over and into the pit. The air flow pattern is intended to over-oxygenate the fire for more complete combustion and to provide a rotating mass of air that acts as a barrier or curtain to reduce the emission of smoke and ash from the fire.
In response to some of the drawbacks associated with open pit burning, a portable incineration apparatus was developed. U.S. Pat. No. 5,415,113, which is assigned to the assignee of the present invention, discloses a portable incineration apparatus that provides an air curtain for reducing the emission of smoke and ash and to provide for more complete combustion of the waste materials. The apparatus provides a box having four walls with a top opening and a bottom opening. The inside of the walls are lined with a layer of a refractory material to form a combustion chamber. The incinerator also includes a source of high velocity air that is in air transfer communication with a manifold assembly. The manifold assembly is adapted to direct an effective sheet or curtain of high velocity air across the top of the opening and down into the combustion chamber and to maintain a substantially uniform discharge rate of the high velocity air as it exits the manifold assembly along the top opening. The high velocity air curtain covers the top opening and creates a rotational turbulence within the combustion chamber. It has been found that because of the substantially uniform discharge rate, the resulting curtain of high velocity air over the top opening limits the amount of particulate, such as ash, released into the atmosphere during combustion and virtually eliminates opacity or smoke.
For both the box and the open pit type of incineration, the burning embers that remain while the incinerator is unattended are a concern. The box or trench is typically unattended at the end of shifts, overnight, on weekends or the like. When the incineration apparatus is shut down, there is normally fire in the box or the trench, and therefore, there is a risk that embers will escape if the wind picks up or if a log should collapse in the fire. If the embers escape, there is a risk of starting a fire outside of the box or trench.
Accordingly, there is a need for a protective device for use with an incineration apparatus.